1. Field of the Invention
The present invention relates to machinery for securing wire terminals to planar work pieces, and particularly, to equipment for inserting and securing electronic components to printed circuit boards (PC boards) by cutting and clinching the lead wires of such electronic components.
2. Prior Art
Mass-produced printed circuit boards common in the electronics industry are circuit-prepared insulative substrates provided with preformed openings. Each opening is carefully positioned and adapted to receive one lead-wire of a variety of electronic components, including resistors, capacitors, transistors, etc. which are intended to be electrically interconnected with the printed circuit formed on the insulative substrate.
It has been found that such electrical components can be quickly and economically inserted into the appropriate openings of the PC board through the use of automatic equipment called "inserters" or insertion machines. A typical insertion machine includes three basic mechanical assemblies which are all connected to a common frame; a head assembly, a work-support assembly, and a clinching assembly. An insertion machine is programmed to rapidly form (or otherwise prepare) the lead wires of various electrical components as they are supplied from adjacent supply bins, cartridges, or from a pre-sequenced supply ribbon and position and insert the lead wires into the proper openings of the PC board. The head assembly, the work-support assembly, and the clinching assembly of a typical insertion machine function together similar to the operation of a desk-top stapler which secures staples to a sheet of paper, wherein each "staple" is analogous to a prepared electrical component and the sheet of "paper" is analogous to a PC board. A PC board is secured to a work-support table. The work-support table, which is usually selectively pivotal, is positioned between the head assembly and the clinching assembly. The head assembly and the work-support table move with respect to each other during operation of the inserter machine to properly align and insert the lead wires of each electrical component into the proper pre-assigned openings of the PC board. The head assembly includes a "lead-former" sub-assembly which is used to cut an individual electrical component from a supply ribbon, for example, and bend the lead wires (assuming an axial-type lead wire arrangement) into a predetermined shape. A pusher sub-assembly called a "driver", which is also located within the head assembly, pushes prepared (formed) electrical components from the lead-former sub-assembly through the properly aligned openings of the PC board.
Prior art insertion machines typically utilize pneumatic linear actuators or motor-driven lead screw assemblies to provide the downward linear motion required to move the driver sub-assembly into contact with a formed electrical component and force it towards the PC board which is secured to the work-support table. Among the problems associated with pneumatic-type actuators of prior art insertion machines include noise, speed limitations and a need for auxiliary means to accommodate varying component body and lead wire diameters. The problems associated with using lead-screw type actuators of prior art insertion machines include the expense of manufacturing and implementing the lead screw components and the difficulty of interfacing the lead screw with certain indexing features.
After each of a pair of lead wires of a particular electrical component is inserted into its respective openings on the PC board, the clinching assembly cuts excess lead wire material and clinches the remaining lead wire portions of the particular electrical component to the PC board to ensure that accurate, reliable and "clean" electrical connections are established.
When all of the desired electrical components are clinched to the PC board in their proper openings, the PC board is removed from the work-support table and moved to undergo subsequent manufacturing processes, including a reflux process during which molten solder is applied to the underside of the PC board to permanently and electrically bond the clinched portions of each lead wire of each electrical component to the actual printed circuit.
The head assemblies of component insertion machines of the type generally described above and under consideration in the present invention are described, for example, in U.S. Pat. No. 3,550,238, U.S. Pat. No. 4,553,323 and U.S. Pat. No. 4,719,810. These patents disclose inserters that are pneumatically and/or servo actuated.
Examples of work-support tables of component insertion machines of the type generally described above and under consideration in the present invention are described in U.S. Pat. No. 4,670,977, U.S. Pat. No. 4,193,186, and U.S. Pat. No. 4,574,660. Examples of clinching devices of component insertion machine of the type generally described above and under consideration in the present invention are described in U.S. Pat. No. 4,584,758, U.S. Pat. No. 4,292,727.
All patents identified herein are hereby incorporated by reference.
It is an object of the present invention to provide an electronic component inserter machine which overcomes the deficiencies of the prior art.
It is another object of the invention to provide a head assembly for use with an electronic component inserter machine which overcomes the deficiencies of prior art head assemblies.
It is another object of the invention to provide a work-support table for use with an electronic component inserter machine which overcomes the deficiencies of prior art work-support tables.
It is another object of the invention to provide a clinching assembly for use with an electronic component inserter machine which overcomes the deficiencies of prior art clinching devices.
It is yet another object of the invention to provide a head assembly having a simple linear drive mechanism which provides smooth reciprocating linear motion to a driver sub-assembly.
It is yet another object of the invention to provide such a linear drive mechanism which concurrently drives a component supply ribbon feed mechanism.
It is yet a further object of the invention to provide a pivotal worksupport table which includes a fast, simplified, and accurate indexing system.
It is yet a further object of the invention to provide a clinching device which automatically determines the present of the leads of an electrical component located within an opening during a cutting operation.